The route initially measured 10 km, stretching from Del Parque station (now the site of the Teatro Colón) to Floresta station, which at that time was located in San José de Flores village, but is now within Buenos Aires city limits. The rails were laid along what are now Lavalle, Enrique S. Discépolo, Avenida Corrientes and Avenida Pueyrredón, and then followed the route of the current Domingo Sarmiento Railway line towards Floresta.

Although the construction of this line was proposed by a group of private individuals known as the "Sociedad del Camino-Ferrocarril al Oeste" (in English: "Western Railway Society"), it was financed by the province of Buenos Aires, which was at that time an independent state of the Argentine Confederation. In 1863 the province became sole owner of the railway line.

The Western Railway was one of the greatest triumphs of Buenos Aires state, which justified its 27 years of ownership of the railway based on the wealth it brought to the city, its efficiency and its lower fares than those of the British-owned railway companies operating in the country. Pressure from British capital and the debts owed by the state of Argentina led to its sale in 1890 to the British company "Buenos Aires Western Railway".

In 1854, while Buenos Aires was an independent state of the Argentine Confederation, governor Pastor Obligado awarded the Buenos Aires Western Railroad Society a grant for constructing a railway, from the city of Buenos Aires towards the west. This grant was fulfilled by a bill presented on 9 January by a financing committee consisting of Dalmacio Vélez Sársfield, Bartolomé Mitre and Mariano Billinghurst.

The railway's importance had already been pointed out by Juan Bautista Alberdi, who wrote in his work Basis and starting point for the Political Organization of the Argentina Republic that "the railway is the means of turning around what the colonizing Spaniards did on this continent".[2]Domingo Faustino Sarmiento and Justo José de Urquiza had also defended the idea. On 17 September 1853 the above-mentioned Railway Society, formed by a group of traders, conscious of the progress in communications which its construction would lead to and the demonstration of power it would represent, requested the grant for constructing a railway which would serve both passengers and cargo and whose cars would be pulled by a steam engine. However, in 1854, when work was about to begin, the Society asked to be exempted from using steam engines arguing that it would be more convenient "to use horses, so cheap in this country, instead of coal, which is so expensive" (this method of powering trains had already been used in Europe). The motive behind this request is not clear, but it may have been because most of the population had never seen a locomotive and believed that this would be dangerous for the surrounding buildings because of the resulting vibration, or perhaps the company considered locomotives to be too costly and the expected number of passengers were low. It must be taken into account that the western railway had no financial guarantee of minimum earnings, as the soon-established British railways would have (among other benefits). They would only earn what they obtained from their own activities. In any case, steam engines were finally purchased.

A law sanctioned by Buenos Aires province's Chamber of Representatives established the donation of public land, free import of supplies and tax exemptions.

Among the engineers who worked on the project were Verger (who created the original plans), Mouillard (a French engineer who was concerned with levelling the route) and, later, William Bragge, who had already built the first railway in Rio de Janeiro. 150 workers were also hired.

A steam engine named La Porteña arrived on 25 December 1856. Built by the firm E. B. Wilson and Company at The Railway Foundry in Leeds, England, it was purchased by the first administrator of the Railroad Company, the engineer Luis Elordi. Its mechanics, the brothers John and Tomas Allan, came with it.

A now-discounted popular legend[3] says the locomotive came via Crimea; for example, Raúl Scalabrini Ortiz wrote in Historia de los Ferrocarriles Argentinos (History of the Argentinian railways) (1940), that "it was built for India and used in the siege of Sevastopol, during the Crimean war. The diffusion of wide gauge railway lines here (unusual within the world) is due to this fortuitous circumstance."[4] However, some historians deny this, and research in the 1950s showed that this story is untenable;[5] for example, Julio A. Luqui Lagleyze does not believe this could be the case, "since it uses a different gauge, and the dates of its construction and entrance into the country leave a gap which would not have allowed this".[6] Others have been of the same opinion, including Vicente O. Cutolo.[7] The works number shows the locomotive left Leeds in 1856, after the demolition of the Crimea railway had already begun.[8] Its dimensions and characteristics would have been unsuitable for the steep gradients in Balaclava,[8] and technical considerations would have prevented conversion from standard to broad gauge.[9]

A carriage pulled by 30 oxen brought the locomotive from the port to the station. The vehicle was of type 0-4-0 ST, reached a speed of close to 25 km/h and weighed 15,750 kg. It remained in use until August 1889, after which is was only used for shunting for ten years. It is currently on exhibit in the Provincial Transport Museum which forms part of the Enrique Udaondo Provincial Museographic Complex in Luján, together with one of the wooden carriages.

The first of the company's mechanics was the Italian Alfonso Covassi,[10] who had one year's experience in the position after having been employed by the company Strada Ferrata Leopoldina, from Tuscany, Italy.

The second engine which worked together with La Porteña was called La Argentina. It was transferred to Paraguay in 1869 by Domingo Sarmiento, together with four other locomotives. The engines were given names such as Rauch, Libertad, Indio amigo and Voy a Chile, the latter named because of a decree in December 1868 which ordered the line to be extended up to the Andes. However, it never reached Chile.

To begin with the train consisted of four carriages, each containing 30 passengers, and a central entrance on one side. The carriages had four axles, were wooden, originally quite luxurious and lit by oil lamps. There were 12 cargo wagons which could each carry up to 5 tons.

Rain prevented the train’s inauguration from occurring in January 1857, as had been planned for, but a successful trial was carried out that month. On 7 April the train derailed during another test, but at a low speed and with no fatalities. In June another test was carried out, and in August a test journey, with one carriage of packages and another of passengers pulled by La Porteña, carried Bartolomé Mitre, Dalmacio Vélez Sársfield, Valentín Alsina, and some members of the Society. The outward journey presented no difficulties, but on the way back excitement lead the mechanic, the British John Allan, to ask for more speed, which led to a derailment by Almagro station breaking several metres of the track. Some of the passengers suffered light injuries. One of the witnesses commented as follows:

The journey was slow and the train reached Floresta with no problems. With the train ready to return and the commissioners pleased with the first trial, they ordered Mr Allan to return at a greater speed until, halfway along the line with the train on an embankment, the train shook, then ran for some distance along the sleepers, breaking 60 or 70 metres of the track. The shock was very violent; Mr Van Praet and Mr Gowland bumped heads, the latter ending up with a bleeding head wound. Mr Moreno was launched headfirst into the body of Mr Llavallol, and Mr Miró, who smoked, ended up with his cigarrette down the back of his neck, burning him under his shirt.

Raquel Fusoni Elordi, granddaughter of Luis Elordi (the above-mentioned company administrator), in a letter to the readers of the newspaper La Prensa dated 10 October 1957, refers to the pre-opening tests thus:

In 1857, after a thousand setbacks, the work was finished. The rails brought from Europe did not reach Flores, so they had to be constructed from wood coated with sheet metal, which jumped every time the train passed over them and the laborers had to run to nail them down again. At one of the tests the convoy derailed, a fact which had to be kept secret in order not to alarm the population. On 30 August the opening was almost suspended, because some drunkards tried to tip La Porteña over, an occurrence prevented by Elordi's opportune intervention.

While most of the population did not find out, those interested in the business did everything possible to stop the accident from becoming known, and it became clear that it was necessary to make some more adjustments before the inauguration.

Another story of a test journey makes it clear that vandalism was another serious problem in carrying out the project. In Los Debates, 7 August 1857, it says:

The route is beautiful. It runs parallel to the main street to Flores, passing estates and fields on both sides, presenting the most beautiful panorama for viewing. We travelled at 20 miles per hour of the 400 "rail" shafts. We had to pass opposite Flores: some miscreant had ripped out one of the hidden crossbars on which the rails rest (...) Just as bad was the removal of poles and wires which surrounded the line in order to keep out horses on Sunday night, which could be seen by their footprints and by the sticks and wires left a short distance away.

On 27 August a new and successful test was carried out. On that day the country’s first telegraph network was also started up, laid out by the company with the aim of helping the rail service.

Finally, on 29 August 1857 (a sunny Saturday) the opening ceremony took place, presided over by the governor of Buenos Aires, Valentín Alsina. On the inaugural journey he was accompanied by, among others, Bartolomé Mitre, Domingo F. Sarmiento, Dalmacio Vélez Sárfield, Estanislao del Campo, members of the Railroad Society and special guests such as local political boss José María Yanquetruz, in military dress.

That morning a mass was celebrated and the engines La Porteña and La Argentina were blessed. La Porteña and its carriages, driven by Alfonso Corazzi (also acting as stoker), was waved off from the decorated station by a crowd, and reached San José de Flores village, were a band played the Marcha a Lavalle. Finally it reached the terminal station, La Floresta, where it was welcomed by a crowd and the company gave a refreshment service to the passengers in the local Café Restaurant.

On 30 August 1857 a regular public service was offered twice a day in each direction. A new night service was apparently soon authorised. A first class ticket was $10, and second or open-carriage tickets were $5. From the first trip until 31 December, 56,190 passengers and 2,257 tons of cargo were transported. In Buenos Aires the population at the time was approximately 170,000 inhabitants. In 1858 the line transported 185,566 passengers and 6,747 tons of cargo.

Real-estate interests came into play when determining the location of the starting station, because of which the meetings, which took place in the home of antiques dealer Manuel José Guerrico, were kept secret. The place finally chosen for the station was opposite the "Plaza del Parque" (known as Plaza General Lavalle since 1878), so named because since 1822 the park’s artillery building was located opposite. The site of the station, named after the park, was approximately the same as the current location of the Teatro Colón, between "Cerrito" (previously "Del Cerrito"), "Tucumán", "Libertad" and "Viamonte" (previously "Temple") streets. The Plaza was merely a gap in the city which, precisely because of the station, began quickly to urbanise its surroundings and improve its appearance with plants and trees.

In 1858 the company offered horse-drawn bus service to allow people to reach the park station from Defensa, Perú and Piedras streets (between Chile and Mexico streets) and from Plaza Concepción.

In the first year of service the route was 10 km long, over a 1,676 m gauge (5' 6"), the same as that used by some colonial English railroads. For the safety of pedestrians the beginning of the train's route was surrounded by two tall sets of railings brought over from England.

The route left Del Parque station towards the west, zigzagging through the square, which provoked serious complaints from neighbours who said that their environments were being invaded, to reach what is now the corner of Talcahuano and Lavalle.

It continued straight on along this last street, passing opposite Artillery Park (now the site of the Palace of Justice) up to Callao boulevard (now Avenida Callao). There it moved in an S shape towards the south-east, bringing it to what is now avenida Corrientes. This S-shaped stretch now memorialises the train’s route with artwork by Marino Santa María on the facades of the buildings on the eastern side.

From Corrientes it continued straight on to Pueyrredón avenue (previously "Centroamérica"), where it turned sharply and continued onto Cangallo (now Juan Domingo Perón), then returned to a westerly heading to enter the West Market (now Plaza Miserere) and the wooden Once de Septiembre (later replaced by the current station), reached by Ecuador to the west and named after 11 September 1852, day of the rebellion of Buenos Aires Province against the Federal Government.

Workshops functioned between Corrientes, Paso, Tucumán and Pueyrredón until 1887. The line then followed a route parallel to present-day Bartolomé Mitre up to the triangle formed by the current streets Medrano, Pelufo and Lezica, where the (also wooden) unmanned station Almagro was located. This area only contained a few scattered farmhouses and ceased to function in 1887.

At that time Medrano street was called the "Camino del Límite" (Boundary Road), which indicated the city limits of Buenos Aires, and on crossing this street the train was then in the administrative area of San José de Flores. Two kilometres further west, on reaching what is now the calle Federico García Lorca (then Caballito and later Cucha Cucha) it found the wood and cardboard station Caballito (named for the pulperia established by Genovese merchant Nicolás Vila in 1804,[13] that had a horse-shaped weather vane on its roof).[14] After crossing Caballito (an area of luxurious estates and houses), and close to Caracas (then called Paz) trains reached the wooden station of San José de Flores, which in 1862 was moved 250 mt. to the west to what is now calle Gral. José Gervasio Artigas (then called Sud América) due to a property dispute with the land owners. The village of Flores only contained a temple, a plaza, small houses and a few businesses.

Continuing to the west, at 10 km from its starting point, between Joaquín V. González (then "Esperanza") and Bahía Blanca (first an unnamed street and then "De La Capilla") it reached Floresta station (wooden). This station was for some time called "Vélez Sársfield", and in 1862 was replaced by a more modern building.

In 1858 it was extended 8 km to Ramos Mejía, in 1859 to Morón and in 1860 to Moreno, with which the route reached 39 km in length.

The financial collaboration of the government of Buenos Aires was decisive in the initial organisation of the company, providing more than one million pesos, renouncing in advance any dividends coming from this sum, and providing another six million pesos to secure the extension of the line. On 1 January 1863 it would become sole proprietor of the company on buying stock from the private individuals, and under its administration the railroad would reach a length of 177 km in 1870. At this point it transported more than 500,000 passengers and 166,551 tons of cargo annually, producing a profit of 9.78% interest over the invested capital.

During the 27 years in which it belonged to the Government of the Province of Buenos Aires, the Western Railway was the line which was most luxurious, least wasteful in its bureaucratic-administrative expenditure and offered the most economical fares and cargo rates. It was a model company which was the pride of the Argentina, in relation to which all the English railway companies established in our country were, without exception, second-rate.

In March 1865 the railway reached Mercedes, than extending to Chivilcoy one year after, without having needed to ask for foreign aid. A Law promulgated in November 1868 obligued the FCO to extend its lines to Andes with the purpose of connecting Atlantic and Pacific oceans routes. While the route to the Andes was studied, the FCO would later extend its tracks to other cities such as Chivilcoy, Bragado, 9 de Julio, Pehuajó and Trenque Lauquen. The FCO also projected a line from Merlo to Aires and then to Azul, but the Great Southern Railway proposed in 1871 to extended its line (that had reached Chascomús in 1865) from that city to Dolores then reaching Azul. The Provincial Legislature approved the project brought by BAGSR in 1872, so the FCO had to dismiss its own project.

In 1871, during the epidemic of yellow fever in Buenos Aires, a railway line was added to function as a receiver of coffins. This branch left from Bermejo station, located on the south-east corner of the homonymous street (now Jean Jaurés) and Avenida Corrientes, and reached what is now the Parque Los Andes, where there was a cemetery which was later moved to the current La Chacarita Cemetery. It was known as the "train of death", and as well as the mortuary in Bermejo there were two others located on the south-east corners of Corrientes and Medrano and of Corrientes and Avenida Raúl Scalabrini Ortiz (then called Camino Ministro Inglés). John Allan, the above-mentioned first driver of La Porteña, drove this gloomy train and fell victim to the epidemic at the age of 36.

In 1873 the convenience of raising the tracks between Plaza del Parque terminus and Once de Septiembre station was already under consideration, due to the vast urbanisation which had taken place along this route making the train’s passage dangerous. The FCO reached Bragado in 1877. On December 20, 1882, the new Once station building was inaugurated. A municipal decree in April 1878 decided to move the terminus to Once de Septiembre but the company delayed its response to the request, despite a concurrent claim from the neighbourhood, until 1 January 1883. By 1879 the railway network totalized 297 km. That same year the net profit was $ 16,788,000. Four years later, the rail network increased to 583 km, with a net profit of $ 21,583,000; in 1885 the FCO totalized 892 km of tracks.

In June 1884 the offices of the Army's General Staff were installed in the Del Parque station building. On 13 September 1886 the Deliberative Council authorised the quartermaster to demolish the building and build the new Teatro Colón on the same site, works which began in April 1890. The theatre remains in this location today. In its place, in the same year the building which replaced the wooden station of Once de Septiembre were also built.

The British were pressing to obtain the railroad at a low price. They had good reason for this, which was not related to earnings from its operation but rather to what was said by the British government minister in Buenos Aires, Thorton, in a report to the Foreign Office. This document, referring to the creation of the British line "Gran Sur de Buenos Aires", pointed out that this company "would open up a new market for British manufactured products." [15] In effect, locomotives, bricks, bridges, sanitation tools for the stations, etc. were imported from Great Britain. So were large quantities of a non-manufactured product: the coal for the engines.

Three months after Juárez Celman became president of Argentina (1886–1890), the main line of the Ferrocarril Andino was sold to a British company. In 1887 the Central Norte was sold, and soon after so was the Western Railway. In his presidential speech of 1887 he announced: "I am planning to sell all public, reproductive works in order to pay our debts, because I am convinced that the State is the worst administrator".

In 1887 the Western Railway has already been condemned to death (...) The unnecessary growth in spending, largely due to the disproportionate increase in employees, the unavoidable increase in capital invested in construction, the resulting decrease in returns and the rise in ticket prices made up a definite intent to sabotage: the Western Railway would quickly be discredited in the public opinion. Fares were increased by 25%, and were still lower than those of the British railways.

By 1887 the FCO network extended to 1,022 km, increasing to 1,210 km two years later, until reaching Trenque Lauquen in 1890 prior to its sell to a British company.

In 1888 the province sold a section of the Western Railway network close to La Plata to the Buenos Aires and Ensenada Port Railway. The National Government made a call for tender by decree in December 1889, for the sale of FCO at a minumum price of $ 34,068,728. The entire line was put into sale with the exception of the branch from Tolosa to La Plata. The Témperley-Cañuelas line had been sold to Alejandro Henderson of BAGSR for $ 760,000. Finally, on April 29, 1890, the Ferrocarril del Oeste was officially sold to H.G. Anderson on behalf of Buenos Aires Western Railway Ltd. at £ 8,134,920, equivalent to 4 million stamped gold pesos.

The governor argued that millions of gold pesos would "come from abroad to increase public wealth", to be "invested in drainage and irrigation, general and municipal roads and health and surfacing projects". According to Raúl Scalabrini Ortiz: "Needless to say, the small amounts of money gained by the sale of the Western were never used for such ends". Historian William Rögind found the sale of the railway to be imposed by the "wasteful provincial administration", at that time headed by governor Julio Costa. Historian H. S. Ferns pointed out that "the results of the sale could not save the province's financial situation".

Once a "cuarteador" challenged the steam engine to a tug-of-war with his horse, which was a champion at this game. It seemed at first that the horse was winning, but in reality it was a prank by the mechanics who had deliberately reversed in order to make him believe he was winning, only to immediately change direction and win, violently ripping the rope apart at the same time.

"...there was no lack of curious episodes, such as the boy who lay down on the tracks for a bet, the train passing over him, and chief Yanquetruz who on entering the train looked for where the coal-eating, fire-breathing horse was hidden..."
(Pastor Servando Obligado in "Tradiciones de Buenos Aires".)

"...At night a carriage carrying a family ran the same risk. It came in at Paraná corner, and halfway across the square it was surprised by the train which leaves Park station at 9.25 pm. There would have been no avoiding it if the carriage had not managed to mount the pavement on the left. The carriage driver was not afraid, and with a few good lashes of the whip managed to urge his nags to the mentioned task. It was time. The train passed by, grazing the carriage’s wheels. The reader can imagine the unpleasant moment which the family within the carriage passed. To avoid a repeat of these mishaps or worse, guardrails should be recommended on this street to stop the entrance of all types of vehicle five minutes before the train is supposed to cross it. "
(La Nación, 16 August 1882).

For the steam engines to run well, pure water was a requirement. In 1856, as proposed by Eduardo Madero, the Western Railway decided to increase the bore of pipe which transported water to the filters from Recoleta to Park Station, in order to also provide water to the rest of the neighbourhood. This private undertaking became the first pure water service in the city, which until then had only been provided with rainwater or water brought by water carriers.